.arcconfig

export: don't prefetch *all* files in manifest

`hg export` only shows changed files, not all files, but we still
prefetched all files in cmdutil.export(). The same is true for the
other commands calling cmdutil.exportfile(). That meant that `hg
export` with remotefilelog (or lfs, I assume) could take much longer
than expected because it would download all the files in the repo.

Differential Revision: https://phab.mercurial-scm.org/D6532

{
    "conduit_uri": "https://phab.mercurial-scm.org/api",
    "repository.callsign": "HG",
    "arc.land.onto.default": "@",
    "base": "hg:.^"
}